BRATTLEBORO — The Vermont Yankee nuclear power plant developed a small steam leak Wednesday in a key safety system, but Entergy said Thursday the leak was quickly fixed.

If Entergy hadn’t been able to fix the leak in 14 days, it would have had to shut down, according to Neil Sheehan, a spokesman for the Nuclear Regulatory Commission.

“There was a small steam leak identified during periodic testing of a high-pressure coolant injection pump yesterday,” Sheehan said Thursday in an email.

He described the pump as a reactor safety system that would be used to inject coolant into the reactor vessel if the reactor had to shut down quickly and there were still high-pressure conditions inside the vessel.

“The leakage put the plant into a 14-day limiting condition of operation, which means the problem would have to be fixed within that period of time” or the whole plant would have to shut down until that had occurred, he added.

He said the NRC resident inspectors assigned to Vermont Yankee reported that a gasket associated with the pump had been replaced, halting the leakage.

Further testing is being performed to ensure the fix was successful.

“If that proves to be the case, the plant would be able to exit the limited condition of operation,” Sheehan said.

Robert Williams, spokesman for Entergy Nuclear, owner of Vermont Yankee, said the leak was discovered during a routine inspection of the backup cooling system.

“Technicians noted a small steam leak on a flange,” Williams said. “They took the pump out of service and we reported it to the NRC. It has since been repaired and retested and it’s back in service.”

It isn’t the first time there have been problems with the high-pressure coolant injection system. During a quarterly test in 2011, there were audible and visual indications of steam leakage. The steam leakage set off a false fire alarm at the plant.

The February 2011 incident caused temperatures to rise in the reactor building and prompted evacuation of the building, according to news reports at the time.

A similar steam leak in April 2011 was reported to the NRC when Entergy workers used the incorrect material for a new gasket on the same high-pressure coolant injection system.